IE 419 1

IE 419 Work Design:

Productivity and Safety

Dr. Andris Freivalds

Class #2

IE 419 2

NEED FOR SAFETY – 5

• Myths, misconceptions– Safety doesn’t sell– Catastrophic failures main concern– Safety slows operations– Safety is human (operator, user) problem– Cheaper to pay insurance (McWane??)– Making product safer increases costs

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NEED FOR SAFETY – 5 cont’

AMOUNT OF SAFETY

CO

ST

S

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IE 419 – Work Design

• Productivity– Productivity tools: PERT, Worker-machine charts, line

balancing, plant layout

– Work measurement: MTM-2, MOST, Work sampling

• Safety– General safety principles: how to recognize & analyze

problem, select & apply remedy

– Quantitative analyses: JSA, fault-tree, cost-benefit

– Legal aspects: Workers Comp, OSHA

– Hazards: recognize & control specific hazards

IE 419 5

PRODUCTIVITY TOOLS

Methods Study = Systematic recording of existing and proposed ways of doing work in order to improve productivity (to improve the job for the operator)

1) Select project

2) Get and present data

3) Analyze data

4) Develop ideal method

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Fig. 2.1 – Steps in Methods Study

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#1 – Select Project Pareto analysis

• aka: 80-20 rule• 80% of problems

from 20% of jobs• Focus on the 20%• Plot in descen-

ding order as cumulative proba-bility distribution

• DesignTools

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#1 – Select Project Gantt Chart

• Horizontal bar chart of activities, shaded if done• A snapshot of the status of all activities• Focus efforts on those that are behind schedule

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METHODS STUDY (Next?)

2) Get and present data

3) Analyze data

4) Develop ideal method• All of these overlap• Use special charts • Quicker, efficient, for IEs• Focus on productivity

improvement

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PERT and CPM (pp. 27-30)

• PERT = Program Evaluation and Review Technique (1950s)– Booz Allen for U.S. government & military– Time has uncertainty– Minimizing time is main goal

• CPM = Critical Path Method (1950s)– DuPont for large scale projects– Time is specified– Trade-off between cost and completion date

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BASICS

• Set of well defined jobs (activities)

• Totality of which defines a project

• Jobs start/stop independently of each other

• Jobs are ordered in specific (technological) sequence

• Forms a graphical network diagram

• Allows computational estimates

IE 419 12

GOALS/QUESTIONS

• How long if every job works out ideally? (optimistic estimate)

• How long if everything goes wrong? (pessimistic estimate)

• With average conditions → likely result

• How can project be shortened at least cost? (trade-offs)

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RULES/PROCEDURES #1

1) List jobs and estimated duration time

2) Draw network diagrama) Arcs or vectors to depict jobs

b) Arrows to indicate direction (progress)

c) Numbered nodes to indicate events

d) Events = start and end of jobs

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RULES/PROCEDURES #2

3) No two jobs can be identified by same nodes 3

a) 1 2 1 2

b) Dummy jobs take no time, no resources

c) Only to show dependency

1 3

2

Job A

Job BUse Dummy Job

Job A

Job B

Job C

Job D

Dummy Job

Job B

Job A

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RULES/PROCEDURES #3

4) Show precedence relationships (IP) clearlya) Jobs B & C both required for Job D

b) Job C not required for Job D (but needed further on)

AC

4

1 2

3 5

BD E

AC

4

1 2

3 5

BD E

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RULES/PROCEDURES #4

• Time = estimated duration of each job– Earliest start time (ES) = such that IP hold– Latest start time (LS) = without delaying project completion– Earliest finish (EF) = ES + time to complete job– Latest finish (LF) = LS + time complete job

• Critical jobs = jobs which delayed, delay project • Float (slack) = difference between ES and LS; time

that noncritical jobs can be ↑, without delaying project

• Critical path = longest path of critical jobs, determines duration of project; zero float

IE 419 17

Ex #1- CRITICAL PATH (Travel Times)

• Two PSU profs (Allen, Booz) drive to Washington DC for a meeting with their contract sponsor (U.S. Army)

• Prof. Allen leaves State College at 8 AM– drives to Philadelphia (KP, 3 hrs)– get materials from subcontractor Lockheed Martin (0.5 hr)– then onto Washington DC (2.5 hrs)

• Prof. Booz leaves State College 8 AM– drives to Pittsburgh (3 hrs)– meets 3rd prof (collaborator) for lunch (2 hrs)– then onto Washington DC (4.5 hrs)

• What is earliest they can meet for dinner?

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Ex. CRITICAL PATH - 2

AllenBooz

3 3

0.5

2

4.5

2.5

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Ex. CRITICAL PATH – 3Network Table

Activity Nodes IP Time

A - drive (SC, Ph) - 3

B – pick up (Ph, LM) A 0.5

C - drive (LM, DC) B 2.5

D - drive (SC, Pi) - 3

E - lunch (Pi, Lu) D 2

F - drive (Lu, DC) E 4.5

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Ex. CRITICAL PATH – 4Network Diagram

Pi Lu3

2

SC

Ph LM

DC

3

0.5

2.5

4.5

Critical Path = 3 + 2 + 4.5 = 9.5

Earliest dinner: 8 + 9.5 = 5:30 PM

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Ex. CRITICAL PATH - 5

• Critical path = 9.5 hours

• Earliest dinner is 5:30 PM

• Allen can leave 3.5 hrs later (11:30 AM)– Or drive more slowly, sightsee– Flexibility or slack in time = float

• Practically: If Booz shortens lunch to 1 hr, then could meet a 4:30 PM

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Ex #2 – CPM and FLOAT (Building a House)

7 major steps in building a house (months):1) A - Design & obtain financing (3)

2) B - Lay foundation (2)

3) C - Order materials (1)

4) D – Build house (3)

5) E – Select paint (1)

6) F – Select carpet (1)

7) G – Finish work (1)

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Ex #2 – CPM and FLOAT - 2

1 2 4 6 7

3

5

A 3

C 1

B 2D 3

E 1 F 1

G 1

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1 2 4 6 7

3

5

A 3

C 1

B 2D 3

E 1 F 1

G 1

#1

#2

#3

#4

Critical Path =

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1 2 4 6 7

3

5

A 3

C 1

B 2D 3

E 1 F 1

G 1

Forward PassES = max (EFi)EF = ES + t

IE 419 26

1 2 4 6 7

3

5

A 3

C 1

B 2D 3

E 1 F 1

G 1

Backward PassLF = min (LSi)LS = LF - t

IE 419 27

Job LS ES LF EF Float

A (1,2)

B (2,3)

C(2,4)

Dum (3,4)

D (4,6) 5 5 8 8 0

E (4,5) 6 5 7 6 1

F (5,6) 7 6 8 7 1

G (6,7) 8 8 9 9 0

Float = LS – ES = LF – EF

1 2 4 6 7

3

5

A 3

C 1

B 2D 3

E 1 F 1

G 1

0,3 0,3

3,5 3,5

3,4 4,5

5,5 5,55,8 5,8

5,6 6,7

6,7 7,8

8,9 8,9

Critical path = all with 0 float =

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1 2 4 6 7

3

5

A 3

C 1

B 2D 3

E 1 F 1

G 1

Crashing – Expediting job, reallocation of resources to shorten project duration